A reed switch as described in Patent Document 1 is used for switching parts such as relays and various sensor parts. A reed switch includes a plurality of reed pieces made of magnetic metal and a cylindrical glass tube filled with a sealed gas or the like, and the reed pieces are fixed to the glass tube such that the reed pieces have their respective one ends inserted into the glass tube in parallel and their respective other ends projecting out of the glass tube (see Patent document 1, the specification, paragraph [0002]). The reed pieces have their respective one ends in the glass tube serving as contact portions which are brought into and out of contact with each other by an electromagnet or the like disposed outside the glass tube (see Patent document 1, the specification, paragraph [0002]).
A representative material of the reed piece is a binary alloy of Fe and Ni referred to as 52 alloy or the like (see Patent document 1, the specification, paragraph [0003]). Patent Document 1 proposes a ternary alloy containing Co as a major component and containing Fe and Ni in a specific range.